System and method to characterize and identify operating modes of electric loads

ABSTRACT

A system characterizes and identifies one of a plurality of different operating modes of a number of electric loads. The system includes a processor; a voltage sensor providing a voltage signal for one of the electric loads to the processor; a current sensor providing a current signal for the one electric load to the processor; and a routine executed by the processor and structured to characterize the different operating modes using steady state and voltage-current trajectory features determined from the voltage and current signals, and to identify a particular one of the different operating modes based on a plurality of operating mode membership functions of the steady state and voltage-current trajectory features.

This invention was made with Government support under DE-EE0003911 awarded by the Department of Energy National Energy Technology

Laboratory. The Government has certain rights in this invention.

BACKGROUND Field

The disclosed concept pertains generally to electric loads and, more particularly, to methods of characterizing and identifying operating modes of electric loads. The disclosed concept also pertains to systems for characterizing and identifying operating modes of electric loads.

BACKGROUND INFORMATION

Power consumption monitoring and energy management of plug-in electric loads (PELs) inside buildings are often overlooked. By knowing the operating mode (e.g., operating status) of an electric load, energy savings can be achieved with effective management and control thereof. Also, operating mode and energy consumption of electric loads need to be communicated to building management systems in an automatic, low cost and non-intrusive manner.

Electric loads often present unique characteristics in outlet electric signals (i.e., voltage; current; power). Such load characteristics provide a viable mechanism to identify operating status (e.g., without limitation, active; standby) by analyzing the outlet electric signals.

Prior proposals include usage of wavelet coefficients obtained from wavelet transforms and event detection to detect switching of the load. Also, basic power quality related signatures (e.g., one or more of apparent power, cos(phi), active energy, reactive energy, frequency, period, RMS current, instantaneous current, RMS voltage, instantaneous voltage, current harmonic THD (total harmonic distortion) percentage, voltage harmonic THD percentage, spectral content of the current waveform, spectral content of the voltage waveform, spectral content of the active power waveform, spectral content of the reactive power waveform, quality of the network percentage, time, date, temperature, and humidity) are used as a signature to identify a load and its operating status.

For example, a load is in a standby mode when the current value obtained for each load current is less than a percentage of the maximum for each load current in the normal operating state. When an electric appliance plugged into a master socket consumes power less than a suitable threshold (e.g., that of standby power), then those peripheral sockets might be switched off automatically to cut further power consumption. While this may be true for some electric devices, other electric loads (e.g., without limitation, microwaves; refrigerators) have ON-OFF behavior which is a unique internal behavior of the electric load itself (e.g., a desktop computer low power mode). It is not user friendly if the “OFF” cycle of such a device is improperly considered to be a “standby” mode and such load is then turned OFF.

Known prior proposals suffer from several serious disadvantages in terms of accuracy, robustness and applicability, and do not differentiate a parasitic mode or low power mode.

International Pub. WO 2008142173 A1 discloses a method and system for detection of standby status in linear and non-linear loads and automatic disconnection thereof. A “standby state” is detected by detection of the normal operating state of the load, obtaining the maximum value of the current in the operating state, detection of entry into a “standby mode” of the load by establishing the “standby state” when the existing current value obtained in the load is less than a percentage of the maximum value of the current of the load in the normal operating state, starting timing at a determined time for the load when it goes into the “standby mode”, and disconnection of the load and the detection when a value is reached of the timing without the load having returned to the normal operating state.

International Pub. WO 2011091444 A1 discloses automatic detection of appliances. An energy monitoring device is programmed to identify an electrical device coupled to a power supply, and a state of the electrical device, from a change in successive measurements of the power supply. Algorithms for determining a load signature for an electrical device and its state are disclosed. A stored table of load signatures for states is used to identify devices and states. Energy monitoring information is collected and presented to the user on a display, a remote display, or is transmitted over a network to a remote device.

U.S. Pat. Appl. Pub. No. 2013/0138669 discloses a system and method employing a hierarchical load feature database to identify electric load types of different electric loads. The process includes: (1) real-time measuring of current/voltage waveforms of a load being monitored; (2) extracting a high-dimensional feature vector of the load; (3) selecting a first layer feature set, and identifying which load category the monitored load belongs to in the first layer; (4) selecting a second layer feature set (which may be different than the first layer feature set), and identifying which load sub-category the monitored load belongs to in the second layer; and (5) selecting a bottom layer feature set (which may be different than the first and second layer feature sets), and identifying the load type as defined in the bottom layer. Items (3) to (5) provide online identification of the load type. These can also provide online identification of the load operating mode (e.g., without limitation, off, standby, on) and load health.

There is room for improvement in methods of characterizing and identifying operating modes of electric loads.

There is further room for improvement in systems for characterizing and identifying operating modes of electric loads.

SUMMARY

These needs and others are met by embodiments of the disclosed concept, which provides a more meaningful description of different operating modes of an electric device, its characterization, how these characteristics are related to the behavior of the device, and a membership function based algorithm to identify the operating mode of the device. The disclosed concept includes three components: (1) definitions of different operating modes of electric loads; (2) characterization of operating modes using steady state and VI (voltage-current) trajectory features; and (3) a mode detection algorithm for identification of the type of operating mode based on membership functions.

In accordance with one aspect of the disclosed concept, a system characterizes and identifies one of a plurality of different operating modes of a number of electric loads. The system comprises a processor; a voltage sensor providing a voltage signal for one of the electric loads to the processor; a current sensor providing a current signal for such one of the electric loads to the processor; and a routine executed by the processor and structured to characterize the different operating modes using steady state and voltage-current trajectory features determined from the voltage and current signals, and to identify a particular one of the different operating modes based on a plurality of operating mode membership functions of the steady state and voltage-current trajectory features.

As another aspect of the disclosed concept, a method characterizes and identifies one of a plurality of different operating modes of a number of electric loads. The method comprises providing a voltage signal for one of the electric loads to a processor; providing a current signal for the one of the electric loads to the processor; and characterizing by the processor the different operating modes using steady state and voltage-current trajectory features determined from the voltage and current signals, and identifying a particular one of the different operating modes based on a plurality of operating mode membership functions of the steady state and voltage-current trajectory features.

BRIEF DESCRIPTION OF THE DRAWINGS

A full understanding of the disclosed concept can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:

FIG. 1 is a mode transition state diagram in accordance with embodiments of the disclosed concept.

FIG. 2A is a plot of load input current versus time showing different operating modes of a desktop computer in accordance with embodiments of the disclosed concept.

FIGS. 2B and 2C are plots of voltage-current (VI) trajectory of the desktop computer of FIG. 2A during parasitic and operating modes, respectively.

FIG. 3A is a plot of load input current versus time showing different operating modes of an LCD television in accordance with embodiments of the disclosed concept.

FIGS. 3B and 3C are plots of the VI trajectory of the LCD television of FIG. 3A during parasitic and operating modes, respectively.

FIG. 4A is a plot of load input current versus time showing different operating modes of a food processor in accordance with embodiments of the disclosed concept.

FIGS. 4B and 4C are plots of the VI trajectory of the food processor of FIG. 4A during parasitic and operating modes, respectively.

FIGS. 5A and 5B are plots of the VI trajectory of an AC-DC adapter when no load is electrically connected to the adapter in the parasitic mode, and when the load is electrically connected to the adapter in the operating mode, respectively.

FIGS. 6A-6F are plots of the VI trajectory of a battery charger, a bread toaster, a refrigerator, a microwave oven, a space heater and an LCD television during the active mode.

FIG. 7 is a plot of power versus line cycles for a space heater.

FIGS. 8A, 8B and 8C are plots of a sigmoid function (f(x)), an inverted sigmoid function and a double sigmoid function, respectively.

FIG. 9 is a block diagram of an operating mode identification system in accordance with embodiments of the disclosed concept.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality).

As employed herein, the term “processor” shall mean a programmable analog and/or digital device that can store, retrieve, and process data; a computer; a workstation; a personal computer; a controller; a microprocessor; a microcontroller; a microcomputer; a central processing unit; a mainframe computer; a mini-computer; a server; a networked processor; or any suitable processing device or apparatus.

The disclosed concept is described in association with example loads and example load features, although the disclosed concept is applicable to a wide range of loads and a wide range of load features.

The disclosed concept can be employed by power strips, smart power strips, receptacles, outlets, power/energy meters, and power/energy monitoring at a circuit branch level for building energy management. The determined operating mode can minimize unnecessary nuisance trips that result when plugged-in loads are improperly turned off Also, the operating mode information provides visibility to users with power/energy consumption breakdowns by various operating modes. This information provides awareness of how much power/energy is consumed while a load is functioning/operating (or actually in use), and how much energy is still consumed (or wasted) when a load is not really in use. This energy is also called parasitic or vampire energy consumption. This information can identify the potential energy saving opportunities from loads. Furthermore, the information is also helpful to detect failure or health of loads, particularly for those compressor-based loads (e.g., without limitation, refrigerators; coolers) with periodic duty cycles switching between the operating mode and a parasitic/low power mode. The idea is to compare healthy condition mode parameters to faulty mode parameters.

Referring to FIG. 1, a mode transition state diagram is shown. Electric loads show certain mode transition behaviors depending on the types of loads, as well as the user's behaviors. The mode transition state is dependent on the type of event. For FIG. 1, three components (shown in FIG. 9) include a power strip outlet relay (RL) 3, an electric load such as a plugged load (LD) 4, and a power strip (PS) 5. Also, six operating modes include the load operating mode M1, the load low power mode M2 (e.g., without limitation, standby; hibernating; energy saving), the parasitic mode M3 (the load is locally switched off but is still electrically connected to mains power and is still consuming a relatively small amount of power), a mode M4 in which no load is plugged into the PS outlet 20 (FIG. 9), a PS outlet switched off mode M0, and a mode M00 in which the entire PS is plugged off or switched off.

Table 1 shows the modes versus the status of the components.

TABLE 1 Mode RL LD PS Power Remarks M1 ON ON ON +++ Load ID needed M2 ON ON ON ++ Always followed by M1 M3 ON OFF ON + Parasitic mode M4 ON NULL ON 0 RL = ON; Power = 0; no load connected M0 OFF X ON 0 RL = OFF M00 x X OFF x

The following mode transition actions or event definitions are used in FIG. 1. At E1, a load is plugged into an outlet, the load is turned ON and it is locally ON. At E1, a load is plugged out of an outlet and the load is removed when it was locally ON. At E2, a load intelligently switches to low power, and at E2′, the load wakes up from low power. At E3, a load is locally turned off from a local mechanism (e.g., without limitation, button; switch), and at E3′, the load is locally turned on from the local mechanism. At E4, a load is plugged into an outlet but is locally off, and at E4′, the load is plugged out of the outlet when it was locally off. At E0, the outlet relay OR is switched ON/OFF. At E5, the entire power strip PS is plugged into a wall outlet or is turned on.

For characterization of the operating modes, three features are calculated per Equations 1-3:

$\begin{matrix} {{THD}_{> 7} = \sqrt{\left( \frac{I_{RMS}}{I_{1}} \right)^{2} - 1 - I_{3{\_ {nom}}}^{2} - I_{5{\_ {nom}}}^{2} - I_{7{\_ {nom}}}^{2}}} & \left( {{Eq}.\mspace{14mu} 1} \right) \\ {P_{avg} = {\frac{1}{n}*{\sum\limits_{k = 1}^{n}\; {{v\lbrack k\rbrack} \times {i\lbrack k\rbrack}}}}} & \left( {{Eq}.\mspace{14mu} 2} \right) \\ {A = {\frac{1}{2}{{\sum\limits_{i = 0}^{N - 1}\; \left( {{x_{i}y_{i}} + 1 - x_{i} + {1y_{i}}} \right)}}}} & \left( {{Eq}.\mspace{14mu} 3} \right) \end{matrix}$

wherein:

THD_(>7) is total harmonic distortion greater than the seventh harmonic;

I_(RMS) is RMS current;

I₁ is current at the first harmonic;

I₃ _(_) _(nom) is nominal current at the third harmonic;

I_(5 nom) is nominal current at the fifth harmonic;

I₇ _(_) _(nom), is nominal current at the seventh harmonic;

P_(avg) is average power;

n is an integer number of samples;

k is an integer;

v[k] is the k^(th) voltage sample;

i[k] is the k^(th) current sample;

A is area of a voltage-current (VI) plot;

N is an integer number of samples in the VI plot;

i is an integer; and

x_(i) and y_(i) are the i^(th) normalized voltage and i^(th) normalized current samples, respectively, in the VI plot.

For the no load mode M4, no load is not related to electric loads but is related to power strips or power outlets. In order to non-intrusively know the presence of a load, it is important to distinguish no-load versus with-load conditions. When no load is electrically connected at an outlet, the current waveform pattern is relatively random in nature, it shows low power, and there is relatively high distortion in the current waveform. This can be determined from the current waveform of a suitable number of samples, and the plot of the VI trajectory for a suitable number of samples. In M4 mode, there is a relatively very small amount of power measured at an outlet where there is no load connected. The amount of power consumption varies from outlet to outlet. For example and without limitation, real power consumption is less than about 3 W. Also, distortion caused by relatively higher order harmonics is relatively very high. THD_(>7) is relatively very high when the load is in M4 mode. Otherwise, when the load is in the M1 or M3 or M2 mode, distortion caused by greater than the 7^(th) harmonic is not as high as compared to distortion in M4 mode. As a result, real power and THD_(>7) (%) are used for characterization of the no load mode M4.

The parasitic mode M3 occurs when the device is switched OFF from, for example, a local button of the device which is still plugged at the outlet. Electric loads electrically connected at the outlet, but switched OFF, locally consume some amount of power to supply, for example, internal power supplies, LED lights, and circuits energized even when the device is plugged. The load in the parasitic mode can be switched OFF and, thus, identify opportunity for energy savings. For example, power may be consumed by some non-intelligent loads (e.g., without limitation, food processors; bread toasters; coffee makers) because of LED lights and internal power supplies. Similarly, power may be consumed by some intelligent devices (e.g., without limitation, desktop computers; LCD televisions) because of microcontroller circuits that are energized after plug in.

Real power consumed by a load when it is in the parasitic mode is less than real power consumed when the load is in the operating mode. Real power consumed by loads in the parasitic mode is relatively small individually but can have significant impact on the overall building energy consumption. VI trajectory (i.e., a graph or plot of normalized voltage versus normalized current for a single power cycle) gives valuable information about the parasitic mode. The difference in the VI trajectory during the parasitic mode and the operating mode for some of the loads is explained below.

A desktop computer, when connected at the outlet, does initialization and then goes to the parasitic mode. The desktop computer has to be turned ON from a local button and then immediately starts operation of a power-on self-test (e.g., without limitation, memory, keyboard, disk, CDROM) and starts the operating system. Turn ON of the local button depends on the user operation. The desktop computer consumes some amount of power in the parasitic mode because of internal power supplies, LED lights and internal microcontroller circuits energized after plug-in. FIG. 2A shows a waveform including the different operating modes of the desktop computer. Modes M4, M1, M3 and M1 are shown. FIGS. 2B and 2C show the VI trajectory of the desktop computer during the parasitic and operating modes, respectively.

Another example is an LCD television. There are three possibilities when the LCD television is plugged in at the outlet: (1) it can directly go to the operating mode if a signal is available; (2) its local button is OFF, power may be consumed by internal circuitry or LED backlight, and the amount of power consumed may vary from manufacturer to manufacturer and depends on various factors (e.g., without limitation, circuit design; size); and (3) the LCD television is switched OFF from a remote control. FIG. 3A shows a load input current waveform including the different operating modes of the LCD television. Modes M4, M3 and M1 are shown. FIGS. 3B and 3C show the VI trajectory of the LCD television during the parasitic and operating modes, respectively.

A further example is a food processor. When electrically connected at the outlet, the food processor goes to the operating mode M1 only when a user turns ON the local ON button. It operates for a relatively very short time and then goes to the standby mode. FIG. 4A shows a waveform including the different operating modes of the food processor. Modes M3, M1, M3, M1 and M3 are shown. FIGS. 4B and 4C show the VI trajectory of the food processor during the parasitic and operating modes, respectively.

For example, in a food processor type of load, M1 is the mode in which the food processor is actually used for food processing (i.e., ON), by turning ON the knob/button (available on the food processor). The food processor is stopped by again using the knob/button. Thus, when the knob is in the STOP/OFF position, the food processor goes to the M3 parasitic mode, as it is only plugged into the outlet and consuming parasitic power. This is analogous to a desktop PC waiting for a user to use a button to start the same. Additionally, the food processor goes to the parasitic mode M3 by user activity and not on its own, which is not treated as the low power mode M2.

A still further example is an AC-DC adapter or charger. Loads like adapters and chargers do not have a local ON/OFF button. These loads can be said to be switched OFF only when they are plugged OFF from the outlet. For example, a cell phone charger consumes power even when the cell phone battery is fully charged or the cell phone charger is not electrically connected to the cell phone. FIGS. 5A and 5B respectively show the VI trajectory of an adapter when no load is electrically connected to the adapter (parasitic mode) and when the load is electrically connected to the adapter (operating mode).

From the above four examples (FIGS. 2A-2C, 3A-3C, 4A-4C, and 5A-5B), the VI trajectory of the load in the parasitic mode M3 has a relatively larger area than its VI trajectory in the operating mode M1. For a majority of the loads, the area has a negative sign, which occurs when the current lags the voltage. Otherwise, if the current leads the voltage, then the area has a positive sign. For some of the reactive loads, the area has a positive sign in the parasitic mode. The area is proportional to the magnitude of the phase shift between the voltage and the current. Relatively small or minimal real power and relatively large negative area are the features used for identification of the parasitic mode.

The active mode M1 is the mode when the load is actually doing its intended function (i.e., it is in the operating mode). Real power consumption is greater in M1 as compared to M4 and M3 for most of the loads. Power consumption is less in case of some loads like, for example, a cell phone charger or adapter, or a lamp load with a relatively low power rating. Other features, such as THD_(>7), is not as high as that of M4 and the VI trajectory area is less (e.g., a relatively small negative or positive value). FIGS. 6A-6F show the VI trajectory of various loads during the active mode. In FIGS. 6A and 6B, respectively, a battery charger and a bread toaster both have a relatively small negative area. In FIG. 6C, a refrigerator has a positive area. In FIGS. 6D-6F, respectively, each of a microwave oven, a space heater and an LCD television has a relatively small negative area.

In the standby mode M2, this low power mode M2 always follows the active mode M1. Several examples of the low power mode include the energy saver mode of a printer, the screen saving mode of an LCD monitor, an idle mode of a desktop computer, and the ON-OFF behavior of various loads such as, for example, a space heater or an iron. Also, there is a relatively large change in the real power when the load goes from the M1 mode to the M2 mode. This relatively large change in power is used to differentiate the standby mode. Loads like the space heater exhibit ON-OFF behavior, which is the internal behavior of the load as shown by the power profile of FIG. 7.

For the design of the disclosed mode detection algorithm, representative data is collected for various different types of loads including relatively low power through relatively high power loads. Various electric features are calculated for this data. The features distribution is analyzed in histogram plots (not shown) to identify the differentiating features which have clear range boundaries between the different operating modes. The values which are distinct for the particular mode and which do not majorly overlap with other modes are taken as the thresholds for a sigmoid function.

Plots (not shown) are prepared of the distribution of real power, the distribution of THD_(>7), and the distribution of area in respective modes M4, M3 and M1. These plots are generated from raw data files of about 30 load types and about 2000 raw data files (of pre-acquired data). Based on the corresponding thresholds, sigmoid functions are designed. The sigmoid function (f(x)), such as shown in FIG. 8A, is represented by Equation 4:

$\begin{matrix} {{f(x)} = \frac{1}{1 + e^{\frac{- {({x - \alpha})}}{\beta}}}} & \left( {{Eq}.\mspace{14mu} 4} \right) \end{matrix}$

wherein:

α is the center of the sigmoid function for the selected feature;

β is the width of the sigmoid function for the selected feature;

x is the test data point of the selected feature; and

the sigmoid membership function f( ) values are calculated for all input test features for a given cycle of data.

In addition to the example sigmoid function shown in FIG. 8A, other suitable sigmoid functions can include, for example and without limitation, the inverted sigmoid function of FIG. 8B and the double sigmoid function of FIG. 8C.

Table 2 shows non-limiting examples of various membership functions and thresholds used in the disclosed mode detection algorithm:

TABLE 2 Used in the Membership Equation of Feature Function Name Width (a1) Center(c1) Mode: Real Power mf1_1 −1 3 M4 mf1_2 1 2 M1 mf3_1 −1 10 M3 mf5_1 1 12 M1 THD > 7 mf2_1 0.02 200 M4 (%) mf2_2 −0.02 250 M1 Area mf4_1 −5 1.1 M3 mf4_2 5 −1 M1 mf4_3 3.33 2 M3 mf4_4 −3.33 2 M1

The mode detection algorithm main logic for M1, M3 and M4 mode differentiation is a follows:

if(mf5_1(real power) >= 0.7)  mode ID = “M1” else if (area < 0) // negative area  fnAreaMode3 = mf4_1(area)  fnAreaMode1 = mf4_2(area) else // positive area  fnAreaMode3 = mf4_3(area)  fnAreaMode1 = mf4_4(area) end

The probability of the mode being M4, M3 or M1 is calculated from respective Equations 5-7, with the yy[ ] array being sorted in descending order, and the mode with the highest probability being the winner.

yy[0]=mf1_1(realPower)*mf2_1(THD_(>7))   (Eq. 5)

yy[1]=mf3_1(realPower)*fnAreaMode3   (Eq. 6)

yy[2]=mf2_2(THD_(>7))*fnAreaMode1*mf1_2(realPower)   (Eq. 7)

The end results are available in the yy[ ] array, where yy[0] stores the probability of M4, yy[1] stores the probability of M3, and yy[2] stores the probability of M1. The Mode Type ID first winner is the mode with the highest probability in yy[ ], and the Mode Type ID second winner is the mode with the second highest probability in yy[ ]. The Probability difference=1−(probability of second winner/probability of first winner).

The disclosed mode detection algorithm can be enhanced in the event that M4 and M1 might have overlaps. In that instance:

if (mf1_1(realPower) > 0.7 and the highest Probability < 0.3)  Mode ID = “M4” end

The disclosed mode detection algorithm can also be enhanced in the event that M1 and M3 might have overlaps. In that instance:

if (Probability difference < 0.5) if(firstwinner = “M3” and second winner = “M1”)  first winner = “M1”  second winner = “M3”  probability of first winner(confidence level) = 1  probability of second winner(confidence level) = 0.1  Probability difference = 0.9 end end

For M2 detection, M2 is always followed by M1. Thus, in order to detect M2, the load has to go to M1 at least once after its power on. The major difference is only power levels, M2 power is less than M1 power. When the load goes from M1 to M2, the real power step down ratio is <0.5. The logic is:

If the load is detected in ‘M1’ as per the mode detection algorithm main logic and there is a step down ratio of <0.5, then the mode is assigned as ‘M2’.

FIG. 9 shows the example operating mode identification system 2 which characterizes and identifies one of a plurality of different operating modes M1,M2,M3,M4 of a number of electric loads 4. The system 2 includes a processor 6, a voltage sensor (VS) 8 that provides a voltage signal (v(t)) 10 for one of the electric loads to the processor 6, a current sensor (CS) 12 that provides a current signal (i(t)) 14 for the one of the electric loads to the processor 6, and a routine 16 executed by the processor 6. The routine 16 is structured to characterize the different operating modes M1,M2,M3,M4 using steady state and voltage-current trajectory features determined from the voltage and current signals 10,14, and to identify a particular one of the different operating modes based on a plurality of operating mode membership functions (MF) 18 (e.g., without limitation, as shown in Table 2). The example system 2 includes voltage and current sensing from an outlet 20, capturing and storing a line cycle of data of voltage and current, and calculating the needed features from the captured data including real power, current THD and VI trajectory area, applying the example mode detection routine 16, displaying the final mode identification results 21 on the display 22, and repeating the above for the next progressive line cycles as well.

The overall success rate for offline testing using pre-acquired data, real time simulated testing and real time testing on an embedded platform is shown in Table 3.

TABLE 3 Simulated Real Time Offline Testing on Testing Simulated Real Embedded Success Rate Time Testing Platform Success Mode (%) Success Rate (%) Rate (%) No Load (M4) 90 98 100 Parasitic Mode 85 92 95 (M3) Active Mode 99 100 100 (M1) Standby Mode 85 90 92 (M2)

From the above, the disclosed algorithm is able to identify the operating modes with an accuracy of greater than 95% on average.

While for clarity of disclosure reference has been made herein to the example display 22 for displaying, for example, mode identification results, it will be appreciated that such information may be stored, printed on hard copy, be computer modified, or be combined with other data. All such processing shall be deemed to fall within the terms “display” or “displaying” as employed herein.

While specific embodiments of the disclosed concept have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the disclosed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof. 

What is claimed is:
 1. A system to characterize and identify one of a plurality of different operating modes of a number of electric loads, said system comprising: a processor; a sensor providing a voltage signal for one of said electric loads to said processor; a current sensor providing a current signal for said one of said electric loads to said processor; and a routine executed by said processor and structured to characterize said different operating modes using steady state and voltage-current trajectory features determined from said voltage and current signals, and to identify a particular one of said different operating modes based on a plurality of operating mode membership functions of said steady state and voltage-current trajectory features.
 2. The system of claim 1 wherein said different operating modes comprise a no load mode, a parasitic mode, an active mode, and a standby mode.
 3. The system of claim 2 wherein said routine identifies the active mode if a first one of said membership functions of real power of the voltage and current signals is greater than or equal to a predetermined value and otherwise, if area of a voltage-current trajectory plot of the voltage and current signals is negative, determines a first value of a second one of said membership functions of the area for the parasitic mode and a second value of a third one of said membership functions of the area for the active mode, and otherwise, if the area is positive, determines a third value of a fourth one of said membership functions of the area for the parasitic mode and a fourth value of a fifth one of said membership functions of the area for the active mode.
 4. The system of claim 2 wherein said routine calculates a probability of one of said different operating modes from at least one of: (1) a first product of a first one of said membership functions of real power of the voltage and current signals times a second one of said membership functions of total harmonic distortion greater than the seventh harmonic for the no load mode, (2) a second product of a third one of said membership functions of the real power times a fourth one of said membership functions of area of a voltage-current trajectory plot of the voltage and current signals for the parasitic mode, and (3) a third product of a fifth one of said membership functions of total harmonic distortion greater than the seventh harmonic times a sixth one of said membership functions of the area times a seventh one of said membership functions of the real power for the active mode.
 5. The system of claim 4 wherein said routine identifies the no load mode in the event that the first one of said membership functions is greater than a first predetermined value, and the first, second and third products are all less than a second smaller predetermined value.
 6. The system of claim 4 wherein a probability difference is equal to one minus a second largest one of said first, second and third products divided by the largest one of said first, second and third products; and wherein if the probability difference is less than a predetermined value, and if the second product is the largest one of said first, second and third products and the third product is the second largest one of said first, second and third products, then said routine identifies the active mode.
 7. The system of claim 4 wherein after said routine identifies said active mode corresponding to a first value of the real power, if a subsequent second value of the real power is less than half of the first value, then said routine identifies said standby mode.
 8. The system of claim 1 wherein said steady state and voltage-current trajectory features comprise total harmonic distortion greater than the seventh harmonic, average power of the voltage and current signals, and area of a voltage-current trajectory plot of the voltage and current signals.
 9. The system of claim 8 wherein a plurality of said membership functions are employed for each of said steady state and voltage-current trajectory features.
 10. The system of claim 1 wherein said processor, for each line cycle of said voltage and current signals, inputs and stores a line cycle of data from said voltage and current signals, calculates total harmonic distortion greater than the seventh harmonic, average power of the voltage and current signals, and area of a voltage-current trajectory plot of the voltage and current signals from the stored line cycle of data, and displays the identified particular one of said different operating modes.
 11. A method to characterize and identify one of a plurality of different operating modes of a number of electric loads, said method comprising: providing a voltage signal for one of said electric loads to a processor; providing a current signal for said one of said electric loads to said processor; and characterizing by said processor said different operating modes using steady state and voltage-current trajectory features determined from said voltage and current signals, and identifying a particular one of said different operating modes based on a plurality of operating mode membership functions of said steady state and voltage-current trajectory features.
 12. The method of claim 11 further comprising: said different operating modes comprising a no load mode, a parasitic mode, an active mode, and a standby mode.
 13. The method of claim 12 further comprising: identifying the active mode if a first one of said membership functions of real power of the voltage and current signals is greater than or equal to a predetermined value; otherwise, if area of a voltage-current trajectory plot of the voltage and current signals is negative, determining a first value of a second one of said membership functions of the area for the parasitic mode and a second value of a third one of said membership functions of the area for the active mode; and otherwise, if the area is positive, determining a third value of a fourth one of said membership functions of the area for the parasitic mode and a fourth value of a fifth one of said membership functions of the area for the active mode.
 14. The method of claim 1 further comprising: calculating a probability of one of said different operating modes from at least one of: (1) a first product of a first one of said membership functions of real power of the voltage and current signals times a second one of said membership functions of total harmonic distortion greater than the seventh harmonic for the no load mode, (2) a second product of a third one of said membership functions of the real power times a fourth one of said membership functions of area of a voltage-current trajectory plot of the voltage and current signals for the parasitic mode, and (3) a third product of a fifth one of said membership functions of total harmonic distortion greater than the seventh harmonic times a sixth one of said membership functions of the area times a seventh one of said membership functions of the real power for the active mode.
 15. The method of claim 14 further comprising: identifying the no load mode in the event that the first one of said membership functions is greater than a first predetermined value, and the first, second and third products are all less than a smaller second predetermined value.
 16. The method of claim 14 further comprising: employing a probability difference equal to one minus a second largest one of said first, second and third products divided by the largest one of said first, second and third products; and if the probability difference is less than a predetermined value, and if the second product is the largest one of said first, second and third products and the third product is the second largest one of said first, second and third products, then identifying the active mode.
 17. The method of claim 14 further comprising: after identifying said active mode corresponding to a first value of the real power, if a subsequent second value of the real power is less than half of the first value, then identifying said standby mode.
 18. The method of claim 11 further comprising: said steady state and voltage-current trajectory comprising total harmonic distortion greater than the seventh harmonic, average power of the voltage and current signals, and area of a voltage-current trajectory plot of the voltage and current signals.
 19. The method of claim 18 further comprising: employing a plurality of said membership functions for each of said steady state and voltage-current trajectory features.
 20. The method of claim 11 further comprising: for each line cycle of said voltage and current signals: inputting and storing a line cycle of data from said voltage and current signals, calculating total harmonic distortion greater than the seventh harmonic, average power of the voltage and current signals, and area of a voltage-current trajectory plot of the voltage and current signals from the stored line cycle of data, and displaying the identified particular one of said different operating modes. 